Ether preparation and recovery from direct hydration of olefins



Patented Sept. 24,, 1957 ETHER PREPARATION AND RECOVERY FROM DIRECT HYDRATION F OLEFINS E. Wendell Carrier, Cranford, N. J., assignor to EssoResearch and Engineering Company, a corporation of Delaware ApplicationNovember 1, 1955, Serial No. 544,216 Claims. 01. 260-614) This inventionis concerned with thepreparation of an ether, particularly diisopropylether, by olefin hydration and an etficient separation of products usinga hydrocarbon solvent at elevated temperatures and pressures.

Desired ethers can be synthesized directly in a vapor phase reaction ofa C2 to C4 olefin with water at-elevated temperatures and pressures inthe presence of solid or liquid catalysts. To produce the etherselectively rather than the alcohol, it is desirable to feed a highratio of olefin to water, though the high olefin feed ratio tends toresult in a' low conversion of olefin during the hydration. With the lowconversion of olefin, the ether, alcohol and polymer products formed areobtained as a complex vapor mixture with the unreacted portion of thefeed gases which may contain also inert hydrocarbon diluents.

In accordance with the present invention, it has been found that theolefin hydration to ether can be improved with a special absorptionrecovery of the ether from the vapor mixture discharged from thereactionzone. This recovery step is important because large amounts of unreactedolefins are to be separated, and recycled to the reaction zone in orderto obtain practical utilization of the raw material. g

The conventional way of recovering products from an olefin hydrationinvolves cooling the vapor product mixture to a relatively lowtemperature in order to condense a substantial part of the ether,alcohol and hydro carbon oil products togetherwith a substantial amountof the residual water vapor. Such an operation is unsuitable at lowolefin conversion levels because large heat losses are incurred by thevajor mixture in cooling to condensing temperatures. In the prior artprocesses to effect recycling of unreacted olefin, substantial heatingwould be required due to this cooling operation, to maintain proper heatbalance and hydration temperatures.

Using the present invention, close control of the operation is obtainedso that higher yields of ether are obtained with heat economy. Theseobjects are attained by scrubbing the complex vapor product mixture witha mixture of liquid hydrocarbons which can be relatively volatile, suchas motor or aviation gasoline base stocks. It is possible by adjustingthe quality and quantity of the hydrocarbon solvent supplied to thehighpressure scrubber to obtain a hydrocarbon extract that has a verysatisfactory quantity of ether, alcohol and polymer for imparting highantiknock value to fuel blends.

If purified or technical grades of the ether product are desired, thehydrocarbon solution of the ether withdrawn from the scrubber may befractionated to effect the purification. For this purpose thehydrocarbon solvent should preferably have a boiling range of about 200F. to 300 F., and may be recycled to the scrubbing zone from apurification tower where the ether is distilled.

Olefins containing from 2 to 4 carbon atoms, e. g., ethylene, propylene,butylenes and mixtures thereof may comprise the reactants of the instantprocess. The reaction conditions will vary somewhatdepending on theparticular olefinselected. The olefin feed as well as the product,inithe-reaction zone will be maintained in the. vapor phase. Generallythe vapor phase catalytic. hydration of.C2-C4 olefins will requiretemperatures between about:-200 -F. to 700 F. and elevated pressures ofabout l00zto 3500 p; s. i. g.

The present. process is particularly applicable to the production. ofdiisopropyl ether by direct catalytic hy-- 'dration of propylene attemperatures between 200 F.. and 700 F. and at elevated pressures ofabout to- 2500 p. s. i. g. with a high ratio of propylene to water vaporin the feed. The types of catalyst used inthe reaction zone are thosesolids which have acid proper ties desirable for synthesis of alcohols,but preferably modified to promote dehydration of the alcohol to ether;for example, mixed catalysts like tungsten-dioxide-tungstentrioxide-alumina (W2O5Al203) or tungsten oxides=titania (WzO5-Ti0z).Other conventional hydration catalysts may be used. Many which can beused are shown in the prior art. Suitable proportions for the reactantsand catalysts in terms of velocity of the feed stream are in the orderof l000-10,000 volumes of gas feed at standard conditions per volume ofcatalyst per hour.

Unexpectedly, it has been discovered that the liquid hydrocarbon solventused, under the specific elevated temperatures and pressures in thescrubbing or absorption zone, effectively separates ether, alcohol andpolymer products from a gaseous reaction product stream containing largeamounts of unreacted olefin, inert hydrocarbon and water vapor. Theeffective temperatures and pres-- sures in the absorption zone are nowfound to be of thethe hydration reaction zone.

A flow sheet diagram is attached for describing a;

preferred embodiment of the invention.

In the process shown by the flow diagram, the propy-- .lene feed issupplied from line 1 by compressor 2 to the;

reactor 3. The required amount of water reactant from:

line 4 is vaporized and superheated in heater 5 and passed by line 6into the reactor 3. A major part of the hydrocarbon reactant enteringthe reactor 3 comes from the recycle stream which enters reactor 3through line 7; and the method of obtaining these recycle streams willbe described in further detail.

The reaction product mixture at elevated temperatures and pressures ispassed directly from the outlet end of the reactor 3 through line 8 to ahigh pressure and high temperature absorber 9. The hydrocarbon naphthafraction solvent is supplied to an upper part of the scrubber tower 9through line 10 under high pressure and at suitable temperatures tomaintain a high temperature and pressure in the absorber, preferablytemperatures and pressures close to those prevailing in the reactor 3.Under such conditions the hydrocarbon solvent supplied in suitablequantity can scrub out practically all the propylene polymer, nearly allthe ether and most'of the alcohol, while leaving most of the inert gasesand unreacted propylene in the gaseous phase to be removed overhead fromthe absorber through line 11. A portion of'this overhead unabsorbed gasis to be bled from the system through flow outlet line 12 to keep inertpropane or other hydrocarbons from accumulating in the system. Thisbleed gas can be sent to fractionating columns for reconcentrating thepropylene to about the same concentration as in the fresh feed, in whichcase it would again become a part of the fresh hydrocarbon feed to thereactor. The remaining portion of the overhead unabsorbed gas relativelyrich in propylene, alcohol and water is passed from overhead line 11through line 13 to booster compressor 14- for recyclingthrough =-1ine 7into the reactor 3.

The scrubber solution of extracted products is with:

drawn from the bottomof absorbent! throu'glrfvalved; line 15 to t hestabilizer tower 16 *Where under partially' 're' duced pressure andtemperature thehydrocarbon solution is stripped of low-boilinghydrocarbons and a subs tantial amountof absorbed water The overheadvapors from stabilizer-tower 16 may be partially condensed in condenserJ7 and refluxed"by' means of line 18.".The'net overhead product inexcessof the reflux containing propylene, propane, and water is returnedthrough line 19- and compressor ZO-tothe recycle line 7 entering reactor3. The bottomsiwithdrawn from;

the stabilizer 16 .by line 21 is the naphthapr gasoline l hydrocarbonsolution containing'lether, alcohol and poly mer with no more than-atrace of water. This gasoline solutionissatisfactory as such foruse as'ablending stock for improving the octane number of motor or aviationfuels.

To-illu strate, a specificoperative embodiment is given in the followingexample2- XA P E A typicaltresh hydrocarbon feed is a C3 cut containing80% propylene and about 20% pi'opane. Enough water vapor is added to thereactor, in addition to that present in the recycle gas from theabsorber, to make the molal ratioof propylene .to water. .in thecombined ,feed" (fresh+recycle). equal. to 4.. The reactor contains ahydration icatalyst comprising tungsten dioxide, tungstentrioxide-Landalumina in a weightratioof 25:25.350. An-

optimum gas velocity is 2000 cu. ft. percua ft. of catalyst perhour-atstandard conditions.

In the present specific exarn'pledirect hydration of pro! pylene isconducted at 3003 F. and 1000p. s. i. g. pressure. Under. theseconditions and at a propylene-water ratio in the .totalafeed-gas of 4,hydration -occurs'win the vapor phase. The conversion of propylene, perpass through the reactor to isopropyl other will amount to.15%', to'isofpropyl alcohol 3%and to propylene polymers 2%. The effluent productpassing.continuously from the reaction zone as vapor is subjected toscrubbing in an absorbertower with gasoline base stock. Per 100.lb1 molsof propylene in the fresh hydrocarbon feed, there will be close to880lb.-:mo1s of reactor eflluent- This quantity of reactor etlluent willbe scrubbed countercurrently with 250ga1lons ofugasolinebase stockwhich. might be by droformate containing aromatics, isoparatfins,naphthenes, and relatively-small amounts of olefins The hydrocarbonsolvent used for scrubbing should be preferably l'owinolefinic-components and in components lower boiling than butane.. Mostsuitable conditions in the absorber are temperatures andpressuresonlyslightlylower. than those maintained .in theireaction zone; 'In thespecific example the absorbenconditions are 280-- F.- and 9852p. s. i.g. pressures Eighty percent of the propylene entering the process in.the freshfhydrocarbon feedis convertedto hydratiorrand.polymerization-products, Pa 100 .lb. mols of propylene in the freshfeed,- there .willbe produced'30.

lb. mols ofdsopropyl ether, 12lb. mols of isopropyl alco hol-and 8ilb.molsof polymer (as propylene). i

In .the. specifieexample, undertheabsorption conditions a given, all thepropylene .polymen nearly all the ether, and.

most-oflthealcohol is scrubbedoutwith the hydrocarbon gasoline .lbase.stockin the. absorber, although aboutT6%.- of the Ca.hydrocarbonsandiasmall amountof water will.

also.be.absorbed. from. the reactor. vaporr To overcomethis...ditficulty,. the. extract, or gasoline solution is fractionatedrat reduced temperatureand pressure to strip out essentially allthe absorbed propaneandfpropylene -together with most ofthe waterfi Therecover'ed C3 hydrocarbons andsmall amount as. water may be compressedto constitute a minor recycle stream to the reja ctor. After'stabilization at a temperature of about 275 F. under a pressure-of about200 p. s. i. g., the ether-alcohol mixture in gasoline should containless than 0.3 volume percent of water.

Twenty percent of the propylene entering the process in the freshfeedstream is removed in the bleed gas after the absorber to purge propanefrom the system which also enters inthe fresh hydrocarbon feed. Thebleed gas may then besubjected'to fractionation, iffdesired, in order toreconcentrate propylene for return to the hydration process.

A typical composition of the vapor from the; absorber recycled to thereactor is as follows based on mols of p py sin t esh qs r o f s a Toproduce blendingstock for improving the octane number. ofrnotor gasolinethe hydroformate selected as the scrubbing agent has a boilingrangebetween and 310? F.japprbiriti1at lyjand an A.'P. I. gravity'ofabout 45.

To obtainla blendsto' cii tori aviation fuelpanalkylatecontainin'gpnly'abo'ntj15%yirgin naphtha (with or without aromaticsy having an j approximate boiling range of l50 3l 0flF. and anAI, P. I.gravity of about 68 may be employed to absorb the hydration products. Ineither case the resulting stabilized blending stock will contain ahighjconc'e itration ofisopropylfether and some 'isopropyl alcohol, andmay then be added in the desired proportions to"gasoline; f0r example,in proportionsbetween 5% and 10%. Alternatively, the ether-containinghydrocarbon extract may be'refractionated' to produce purifiedisopropylether free from alcohol.

This applicationis acontinuation-in-part. oi applic a tion Serial No.451,579,. file d August 23,1954and'now abandoned.

What is claimed is:

1. A process for producing a hydrocarbon solution containing isopropylether which comprises subjecting a mixture containing asubstantialexcess of gaseous propylene to vapor phase reaction withwatenvaporina reaction zone in the presenceof a solid hydration catalystat temperatures in the range'of 200 F. 'to' 700 F, and atpressures'ingthe range off100 to2500 p. s. i. g, passing aresultingigaseousjproduct from the reaction zone into an absorptionzone, contacting said' gaseous productjwithaliquid naphtha hydrocarbonfraction solvent at substantially. the temperature and pressure ofhydration tofetfeet' absorption ofthe ether and ialcohol products,separatingunabsorbedgases from the hydro carbon solutionlcontaining theetherand recycling a major portion of the sepa'rated unabsorbed gasessubstantially under hydrationpressure to said reactiqnfzone.

2. The process defined in clairnl ,Twherein' the gaseous product fromthe reaction'zonecontainsprincipally unreactedpropylene with isopropylether, minor amounts of isopropyl alcohol andpolyrneqand,whereinthe'liqui d' hydrocarbon extract of the ether, alcoholand polymer issubjected to fractionation V under I lowered. temperatures and pressuresto strip out absorbed gases suchas propane and propylene with most ofthewater.

3. The process defined in claim 1, wherein a portion of the gasescontaining :unreacted propylene and any inert gases p'resentunabsorbedbythe liquid hydrocarbon is purged to prevent buildup of the inert gasesin the reaction and absorption zones.

4. The process as defined in claim 1, wherein temperatures and pressuresin the absorptionzone are in the.

5 range of 200 to 700 F. and 100 to 2500 p. s. i. g. but slightly lowerthan those maintained in the reaction zone in order to preferentiallyabsorb the ether product while maintaining the unreacted propylene underhigh pressure for recycling.

5. A process of producing a fuel blending stock containing isopropylether which comprises passing a mixture containing gaseous propylene andwater vapor in a mole ratio of about 4:1 through a reaction zone in thepresence of a solid tungsten oxide hydration catalyst at temperatures ofabout 300 F. and at pressures in the range of about 1000 p. s. i. g.,passing the resulting gaseous product containing isopropyl ether,isopropyl alcohol, unconverted olefin and water from the reaction intoan absorption zone, contacting said gaseous product substantially underreaction zone pressure with a liquid naphtha fraction solvent to effectabsorption of the ether and alcohol products, separating unabsorbedgases substantially under reaction zone pressure from said solvent,recycling a major portion of the separated gases substantially underreaction zone pressure to said reaction zone, and fractionating theremaining liquid naphtha fraction solvent containing absorbed ether toseparate low boiling hydrocarbons, inert gases and a substantial amountof water from the remaining ether-containing naphtha.

References Cited in the file of this patent UNITED STATES PATENTS1,873,536 Brown et a1. Aug. 23, 1932 2,178,186 Oldershaw Oct. 31, 19392,367,479 Wolk Jan. 16, 1945

1. A PROCESS FOR PRODUCING A HYDROCARBON SOLUTION CONTAINING ISOPROYLETHER WHICH COMPRISES SUBJECTING A MIXTURE CONTAINING A SUBSTANTIALEXCESS OF GASEOUS PROPYLENE TO VAPOR PHASE REACTION WITH WATER VAPOR INA REACTION ZONE IN THE PRESENCE OF A SOLID HYDRATION CATALYST ATTEMPERATURES IN THE RANGE OF 200*F. TO 700*F. AND AT PRESSURES IN THERANGE OF 100 TO 2500 P.S.I.G., PASSING A RESULTING GASEOUS PRODUCT FROMTHE REACTION ZONE INTO AN ABSORPTION ZONE, CONTACTING SAID GASEOUSPRODUCT WITH A LIQUID NAPHTHA HYDROCARBON FRACTION SOLVENT ATSUBSTANTIALLY THE TEMPERATURE AND PRESSURE OF HYDRATION TO EFFECTABSORPTION OF THE ETHER AND ALCOHOL PRODUCT, SEPARATING UNABSORBED GASESFROM THE HYDROCARBON SOLUTION CONTAINING THE ETHER AND RECYCLING A MAJORPORTION OF THE SEPARATE UNABSORBED GASES SUBSTANTIALLY UNDER HYDRATIONPRESSURE TO SAID REACTION ZONE.